X-ray images can be taken with film in traditional radiography, they can be digitally generated using imaging plates in a process called computed radiography, and digital images can be generated directly from the X-rays themselves in a process called direct digital radiography. Each of these systems has its drawbacks. When film is used to process X-rays, the film must be purchased for each X-ray, and the film must be developed in a process that takes somewhere around 90 seconds to 5 minutes per shot. A patient must wait for the entire developing time to determine if an image is clear or if a retake is needed. Furthermore, processing the films requires that noxious chemicals be used and stored, and disposed.
Computed radiography removes the film from the X-ray process, replacing it instead with a digital imaging plate the same dimensions as the film and placed in the same location. After the imaging plate is exposed to the X-rays, it is placed in an imaging reader, which takes about 90 seconds to generate the digital image. This delay, while not insurmountable when human adults are having their X-rays taken, is much more problematic when the X-ray subject is a small child or an animal which does not understand the need to remain quiet and positioned. Furthermore, the imaging plate is expensive and fragile, an expensive imaging reader must also be used, and generating the digital X-ray image takes roughly the same time as in conventional radiography.
Direct digital radiography uses an imaging sensor in the path of the X-rays to take a direct digital X-ray, which can then immediately be displayed on a computer screen and saved in a digital file for easy reference. However, it is difficult to adequately shield the imaging sensor from the X-rays, requiring that this expensive piece of equipment be regularly replaced. Moreover, there must be an electrical connection between the imaging sensor and the X-ray generator, making retrofitting existing X-ray equipment difficult or impossible.